In general, a substrate processing apparatus for performing plasma process, such as etching, film-forming or the like, on a substrate, e.g., a semiconductor wafer (hereinafter referred to as “wafer”) has a mounting table for mounting the wafer thereon in a processing chamber. A plurality of ring-shaped members is disposed on the mounting table. One example of the ring-shaped members is a focus ring disposed to surround the wafer on the mounting table. The focus ring serves to expand the distribution area of plasma generated above the wafer to above the focus ring as well as the wafer so that, e.g., the uniformity of etching performed over the entire surface of the wafer can be secured.
Since the focus ring as well as the wafer is directly exposed to the plasma, its temperature increases due to heat generated by the plasma. Accordingly, a temperature of the mounting table is controlled to adjust a temperature of the focus ring as well as a temperature of the wafer.
However, when heat transfer efficiency between the mounting table and the focus ring is poor, it is difficult to control the temperature of the focus ring. Therefore, a heat transfer sheet has been recently disposed between the mounting table and the focus ring to enhance adhesion therebetween, thereby increasing the heat transfer efficiency (see, e.g., Japanese Patent Application Publication No. 2008-171899 (JP2008-171899A)).
However, since the heat transfer sheet is made of, for example, silicone rubber and the like, when it is adhered to the focus ring made of a metal material such as aluminum or the like, air bubbles are easily generated between the heat transfer sheet and the focus ring. If air bubbles are generated, the air bubbles serve as an insulating layer. Thus, the heat transfer efficiency of the mounting table (susceptor) is reduced, which deteriorates the temperature control efficiency of the mounting table. Accordingly, the temperature of the focus ring becomes partially high due to the heat of plasma and the like, which decreases the in-plane uniformity of a plasma process characteristic such as an etching characteristic.
In this regard, for example, as disclosed in JP2008-171899A, there has been proposed a technology in which while the heat transfer sheet is interposed between the focus ring and the mounting table, fine air bubbles dispersedly existing in the heat transfer sheet inflate to become concentrated under a vacuum pressure state, and then the concentrated air bubbles are removed by bringing the vacuum pressure state back to an atmospheric pressure state from (see, e.g., JP2008-171899A).
However, the amount of the air bubbles and locations where the air bubbles are generated depend on an installation state of the heat transfer sheet. Thus, the air bubbles cannot be completely removed by the pressure control as in JP2008-171899A because conditions of the air bubbles are changed depending on the initial installation state of the heat transfer sheet.